The present invention relates to a method of setting the axial position of a sleeve in a rolling mill including at least one roll on which said sleeve is loosely positioned in such a way that the sleeve is revolvable and axially shiftable with respect to the outer circumferential surface of the barrel of the associated roll, said sleeved roll being subjected to a rolling load from one side of the sleeve directed toward the sleeve center onto the outer circumferential surface of said roll barrel along a straight line parallel to the roll axis and which contacts the inner surface of the sleeve with the barrel of the roll, and the roll necks of the roll being subjected to a balancing force for the load through bearing means.
With conventional multiple rolling mills it has been customary to control the flatness and crown of the product by correcting the deflections of the upper and lower working rolls by the applicaton of roll bending forces between those rolls. However, this practice has failed to achieve completely the desired effect because the control functions are limited by the contact of the working roll shoulders with the surfaces of the back-up rolls. Japanese Laid-Open Patent Publication Nos. 103058/76 and 97353/77 proposes methods of controlling the crown of a plate material by positioning sleeves on the back-up rolls of a four stage rolling mill, at suitable positions corresponding to the width of the workpiece. According to those inventions, however, the feasibility of shifting the sleeve positions in order to roll workpieces in varied widths has been considered questionable. More recently, attempts to solve this question have been made as disclosed by Japanese Laid-Open Patent Publication Nos. 48051/78 and 48052/78. These inventions propose rolling mills having a construction generally as shown in FIGS. 1 (a) and (b), in which sleeves 4 and 4' are loosely positioned on the outer circumferential surfaces of back-up rolls 3 and 3' and adjustment of sleeve-supporting arms permits the sleeves 4 and 4' to be suitably shifted in the axial directions of the rolls according to the width of the workpiece 1 to be rolled, changing the degree of restriction on the shoulders of the working rolls 2 and 2' and thereby controlling the deflections of those rolls. In addition, the effect of the roll bending method is enhanced and the life of the back-up rolls is greatly extended. Thus, the latter publications disclose that the sleeves 4 and 4' are loosely carried by the back-up rolls 3 and 3' and the arms supporting the sleeves 4 and 4' are shifted in the axial directions of the rolls by screw or fluid pressure cylinder means.
As compared with the former two inventions, the latter two publications are distinguished by a construction in which each sleeve 4 is loosely positioned on the associated roll 3 with free space provided between them, so that the sleeve 4 can be shifted axially with respect to the roll according to the width of the workpiece 1 to be handled.
Nevertheless, in high speed rolling operation the mills incorporating these inventions still have the following difficulties. The sleeve-supporting arms, which are subjected to heavy loads, must have great strength. Especially during high speed rolling, contact members or the means attached to those arms in order to deliver restricting forces to the sleeves by direct contact, rapidly wear down. Moreover, the contact members develop so much heat due to friction that considerable cooling is an unavoidable necessity.